In order to continuously cast molten metal such as molten steel, the molten steel in ladles is delivered to tundishes for a time and then is delivered to molds.
In order to obtain cast pieces high in purity, sufficiently floating and separating non-metal inclusions in the molten steel delivered to the tundishes from the ladles is essential. In order to sufficiently float and separate the non-metal inclusions, conditions known as short circuiting and high speed flows of the molten steel in the tundishes have to be controlled. The short circuiting refers to the shortest paths molten steel, which is delivered to the tundishes from the ladles, may take to the molds.
Preventive measures against the short circuiting include disposing weirs in the tundishes. The weirs are obstacles against the incoming molten steel, which is delivered to the tundishes from the ladles, to reach immersion nozzles, thereby preventing short circuiting. Also, the weirs lengthen paths the streams of molten steel, which is delivered to the tundishes, take to the molds, thereby promoting the float and separation of the non-metal inclusions in the molten steel.
Unfortunately, however, the weirs do not always control speeds produced by upward streams of the molten steel, which is delivered to the tundishes, which impacts bottoms of the tundishes, and which rebounds upward. High speed upward streams or high speed streams toward side walls of the tundishes posterior to the upward streams may promote slag entrainment on a surface of bath or may shorten time for the streams of the molten steel to pour into the molds. As a result, this configuration does not leave sufficient time for the float and separation of the non-metal inclusions.
In this connection, a weir 4 shown in FIG. 1 has been disclosed (see, for example, Patent document 1).